In the Sense+Solar case I would contend that the measurement made upstream of the meter is not the same as measuring at the breaker (ignoring my 2x problem for the moment) see here Provide ability for Sense to double actual incoming power - #5 by apeterdavies
I might take this follow-on discussion to another thread, because it has diverged from the main topic.
In Sense-land there are two possible mathematical setups for simple solar (simple = no batteries, single solar and mains feeds):
-
Breaker fed or Service-side tap, Configuration A - In this case the mains CTs are measuring Net Usage of your house, and the solar CTs measure solar feed-in. In this case, Sense sums Solar plus Mains CTs to get Total Usage (note that the Mains in the signal section reflects already added Solar plus Mains, not the raw measurement of the mains, which occasionally proves confusing).
-
Service-side tap, Configuration B - Less common - In this case, the mains CTs are measuring the House Total Usage, the the solar CTs measure solar feed-in. So in this setup, the Total Usage comes directly from the mains CT measurements, no addition required.
So your statement above is a little ambiguous - you should really be talking about whether your mains CTs are on the house-side, or the service-side of the breaker - that’s where the difference lies. If your mains CTs are on the house-side (CTs downstream from the solar feed-in), then you are measuring Total Usage. If they are on the service-side (CTs upstream from the solar feed-in), then you are measuring Net Usage.
I’m having newbie navigation problems ie not sure if/how to move a discussion to a different thread…
But sticking here in this thread for a tiny bit longer…
Yup, I like that A and B configuration definition in the Help section. Presumably in either case the Sense+Solar box can automatically detect which configuration is in play. Is this correct? If so the suggestion to “punch a hole” in the meter side and clamp upstream of the meter would work just fine (except for breaking the utility company seal)
(I think I have the less common configuration B)
@apeterdavies,
Let’s keep following this:
- Sense Solar generally does a good job identifying and separately configuring the Breaker fed/Service-side tap A and the Service-side tap B (which puts the mains CTs on the house side), during setup. But you won’t know which you have from any data available in the Sense app.
- And yes, B configuration seems to be less common.
- I would like to understand more about the point A and point B you are describing, before commenting. Do you have a Service-side tap feeding in your solar ? Are you talking then about CONFIGURATION A and B ? Maybe you can include a photo ? And when you are talking about readings at A and B, are you talking about Sense measurements take with the CTs in both positions ?
- And again, I have a Breaker fed configuration, but with a 400A bus that splits into 2 200A busses immediately outside the meter, so I had no choice but to install before the meter box. Sense didn’t have the 2x200 option then and even if they did, I was already using the 2nd set of CTs for solar.
I have never seen a hookup “upstream of the meter”
It is always at the customer side on the meter which I would call “downstream of the meter”
hi kevin1 and dannyterhaar,
thanks for bearing with me as i struggle with consistent jargon…
some pics to help me describe my setup:
overview
(notice intact lead seal beneath meter.
)
cover off: illustrating the ganged 2 by 100Amp breakers and the CT clamps attached to measure “whole home” power drain. even with two sets of clamps there is no physical room to attached the 2nd set. Even the one set looks awfully jammed in place. this results in the 50% measurement.
cover off: looking at the top, solar input breaker.
now, the following images are NOT of my installation but included just to illustrate a potential point for CT clamp monitoring “upstream” of the meter. ie see image bottom right as beneath the meter would be a point where the clamps would be able to physically fit and be able to capture 100% rather than the 50% of the power to/from the grid. this is the so called “punch a hole through to the meter side” approach - way too cavalier for me.
also look at the left side image of the breaker panels with the meter side exposed (no meter installed) this gives some insight in to where the solar input is attached and see the relevant schematic:
(schematic is from inside MY breaker panel).
it would seem the non-solar CT clamps are monitoring the “whole home” electrical load but measuring just 50% of it. the solar CT clamps are measuring 100% of the solar contribution to the “whole home” or the grid.
i’m now really confused as to whether this is config A or config B so would welcome anyone’s explanation of how i am now configured and any clever ideas for monitoring the flow across the entire 200A breaker, not just half of it.
Useful photos. My take is that your do indeed have a Service-side tap type configuration B, though your “tap” is really built into your Siemens land center - your solar and mains are “joined” at the house-side terminals of your meter.
In the schematic, you have your mains CTs at the locations in green and the solar at the locations in orange. I agree that you can’t get the CTs around both cables in your current location. But you might be able to in one of the two locations in magenta, both inside the meter box.
- Top magenta - Type A configuration
- Bottom Magenta - Type B configuration
Thanks for the photos.
Tells a 1000 words
suppy slide for sure
I installed a sense unit for a customer in a similar setup and I did punch a hole through the divisor in bottom middle and connected the main clamps on the supply lines before the meter.
You will have to break the lead seal though. Since you are not interrupting the energy to the house nobody will ever know.
There is a 2nd option: get a 2nd set of MAIN CT’s from Sense and somehow put those around the 2nd red & black wires (impossible to do imo) and hook those up in parallel with the existing ones.
If I have to choose between these 2 options I would go for the upstream hookup for sure.
1 Like
To put the clamps in the magenta, he would need to break the seal of the meter and actually pull the meter (utility for sure notices this!) , remove the lid to attach the CT’s. all while live voltage from the utility is there. I would strongly advise against this.
Maybe his pre-meter is very different, but mine is quite safe… I’m guessing that at least one of the two sets of cables is insulated. Not sure about the need to pull the meter.
This topic was automatically closed 365 days after the last reply. New replies are no longer allowed.